Mitt Romney, left, hugs U.S. Sen. Marco Rubio after Rubio introduced him to the crowd during a campaign stop Monday in Miami. Rubio will also do the honors at the convention.

TAMPA — In a showcase role on his party's biggest stage, Florida Sen. Marco Rubio will introduce Mitt Romney for his speech to accept the nomination for president on the last night of the Republican National Convention.

It is an introduction aimed at giving Romney a boost from a rising star in a must-win state, but it will almost certainly further enhance Rubio's standing, too.

New Jersey Gov. Chris Christie, a favorite among fiscal conservatives in the party, will give the keynote address, the convention announced early Tuesday.

"We have an opportunity in Tampa to make clear that if we tell each other the hard truths, tackle the big problems, and make bold choices, we will see America's comeback," Christie, a former federal prosecutor known for his take-no-prisoners speaking style, said in a statement released through the RNC.

Just last week, Rubio was still seen as a possible contender for the No. 2 spot on the Republican ticket. Though Romney chose House Budget Committee Chairman Paul Ryan, the GOP clearly wants the appeal that Rubio — 41 years old, Hispanic, the son of Cuban immigrants, with speaking skills that resonate both with establishment Republicans and tea party insurgents — can bring to the campaign.

And already, Rubio is putting his charisma to use.

On Monday in Miami, he introduced Romney, who in turn mentioned Rubio as much as Ryan, getting big cheers when he did. On Wednesday, Rubio will go to Texas to help raise money for Romney. In a letter to prospective donors, Rubio calls Ryan a "courageous reformer" and an "inspired choice."

There's more to come, said Romney campaign manager Matt Rhoades, who describes Rubio as "an integral part of our campaign."

"We're honored to have him introduce Governor Romney at the Republican National Convention," Rhoades said in a statement released through the convention. "Since the last night of the convention usually has the largest audience, it's a great opportunity to showcase leaders who will play an important role in shaping the future of the Republican Party. Marco Rubio is that kind of leader."

The GOP expects the audience to be huge. Four years ago, Sen. John McCain's acceptance speech drew 38.9 million viewers nationwide, a figure that approaches the viewership of the opening ceremonies at the London Olympics and is similar to the Oscars.

Republican National Committee chairman Reince Priebus called the senator "without a doubt one of America's most dynamic and inspiring leaders."

"It is fitting that he will take on such an important role at our convention in his home state," Priebus said. "Throughout his career, he has shown true dedication to constitutional principles, fiscal responsibility and free enterprise. As the son of immigrants, he has witnessed the promise of the American Dream firsthand and has worked to secure that promise for future generations."

In a statement of his own released through the RNC, Rubio said he's confident Romney and Ryan will "restore great leadership to our country."

"Future generations of Americans depend on the hard work we will do in the weeks and months ahead," he said. "I know that together we will be successful in changing Washington and putting leaders in place who are committed to creating more jobs and opportunities for our people."

During the vetting process for vice president, Rubio repeatedly predicted he wouldn't be Romney's choice, but he benefited from the nonstop speculation that he would. Already, he is mentioned as a possible presidential candidate in 2016, when he will reach the end of his first Senate term.

During the primaries, Rubio endorsed Romney — but after the former Massachusetts governor won Florida's primary and after it became clear that Romney's path to the nomination was inevitable.

Since then, Rubio's support has grown stronger and he stepped up criticism of President Barack Obama.

Times staff writer Alex Leary contributed to this report. Richard Danielson can be reached at Danielson@tampabay.com, (813) 226-3403 or @Danielson_Times on Twitter.